The use of the both sonic and ultrasonic waveforms have been used to evaluate the quality of the cement sheath between the casing wall and formation. A logging tool, which may have one or more sonic and/or ultrasonic receivers and one or more sonic and/or ultrasonic transmitters, is lowered into a wellbore and measurements are taken at various depths. Sonic and/or ultrasonic waves are transmitted from the logging tool in the wellbore, and reflected waves from the casing, cement, and formation are received, recorded, processed, and interpreted to determine the presence, or lack thereof, of cement between the casing and the formation or other wellbore wall.